The CD-1 mouse is one of the most widely utilized laboratory animal models globally, serving as a workhorse in the biomedical field. This outbred stock is a general-purpose model, meaning it is not bred for a single specific disease or characteristic. Researchers value the CD-1 mouse for its combination of biological stability and genetic diversity, making it a reliable and broadly applicable tool in biomedical research.
Origin and Defining Characteristics
The CD-1 mouse traces its lineage back to the Swiss albino mouse stock, first imported to the United States in 1926 by the Rockefeller Institute. This original group of non-inbred mice was transferred to the Institute of Cancer Research (ICR), where the Ha/ICR strain was established in 1948. The “CD-1” designation is a commercial name associated with this ICR-derived stock, maintained through controlled breeding programs to preserve its outbred characteristics.
These mice exhibit biological hardiness, a significant factor in their widespread use. Female CD-1 mice are known for high reproductive performance, featuring large litter sizes (averaging around 11.5 pups) and excellent maternal characteristics. This robust health profile and high fertility make the CD-1 stock cost-effective and easy to maintain in the large colonies necessary for high-throughput testing. The animals are also docile and easy to handle, benefiting laboratory staff.
The Role of Genetic Variation in Testing
The defining characteristic of the CD-1 mouse is that it is an “outbred” stock, meaning individuals within the population are genetically distinct. This genetic heterogeneity is maintained by breeders, often through systems like International Genetic Standardization (IGS), to prevent inbreeding and genetic uniformity. This contrasts sharply with “inbred” strains, such as the C57BL/6 mouse, where individuals are nearly genetically identical.
The presence of genetic variation in CD-1 mice is valuable because it mimics the diversity found in the outbred human population. Due to this variation, individual CD-1 mice show a range of responses to a given stimulus, such as a drug or compound. For instance, CD-1 mice show wider differences in their liver’s drug-processing enzymes compared to genetically uniform strains, which better reflects human pharmacokinetic variability.
When conducting safety and efficacy tests, this variability is an advantage, as it provides a more realistic assessment of how a compound might affect a genetically diverse group of people. The outbred nature also provides a diverse immune system profile, including a polymorphic Major Histocompatibility Complex (MHC). This makes the CD-1 strain a suitable model for studies where a broad immune response is desirable, such as vaccine development and infectious disease research.
Primary Applications in Research
The combination of genetic variability and physical robustness makes the CD-1 mouse an indispensable model for several types of research, notably in safety and toxicology assessments. Regulatory bodies often require safety studies in a genetically diverse population to predict the range of human responses to new pharmaceuticals or environmental chemicals. The CD-1 mouse is employed in these studies to determine the maximum tolerated dose, evaluate potential toxicity, and identify long-term side effects.
The CD-1 mouse is also a preferred model for general pharmacology screening and efficacy testing. Researchers use the strain to test the effectiveness of new drug candidates, especially when a strong, healthy baseline animal is needed. Their physical resilience allows them to withstand the rigors of long-term studies, providing data on the cumulative impacts of exposure. The CD-1 stock is often used in large-scale production, such as generating biological materials or propagating tumor cell lines, due to their large litter sizes and ease of breeding.